These ‘chips’ often come up on eBay, and are usually nothing more than a single resistor (approximately 2-4,000 Ohm) that you could pick up from RadioShack.
They simply send an incorrect reading to the ecu and make the car run richer, using up more fuel. So it does work in a sense, but not in any meaningful way.
Note these and similar chips exist for many cars, and sometime contain instructions to advance your ignition timing, which can potentially be very dangerous to the health of your motor.